Novel Mouse Xenograft Models Reveal a Critical Role of CD4+ T Cells in the Proliferation of EBV-Infected T and NK Cells

Epstein-Barr virus (EBV), a ubiquitous B-lymphotropic herpesvirus, ectopically infects T or NK cells to cause severe diseases of unknown pathogenesis, including chronic active EBV infection (CAEBV) and EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH). We developed xenograft models of CAEBV and EBV-HLH by transplanting patients' PBMC to immunodeficient mice of the NOD/Shi-scid/IL-2Rγnull strain. In these models, EBV-infected T, NK, or B cells proliferated systemically and reproduced histological characteristics of the two diseases. Analysis of the TCR repertoire expression revealed that identical predominant EBV-infected T-cell clones proliferated in patients and corresponding mice transplanted with their PBMC. Expression of the EBV nuclear antigen 1 (EBNA1), the latent membrane protein 1 (LMP1), and LMP2, but not EBNA2, in the engrafted cells is consistent with the latency II program of EBV gene expression known in CAEBV. High levels of human cytokines, including IL-8, IFN-γ, and RANTES, were detected in the peripheral blood of the model mice, mirroring hypercytokinemia characteristic to both CAEBV and EBV-HLH. Transplantation of individual immunophenotypic subsets isolated from patients' PBMC as well as that of various combinations of these subsets revealed a critical role of CD4+ T cells in the engraftment of EBV-infected T and NK cells. In accordance with this finding, in vivo depletion of CD4+ T cells by the administration of the OKT4 antibody following transplantation of PBMC prevented the engraftment of EBV-infected T and NK cells. This is the first report of animal models of CAEBV and EBV-HLH that are expected to be useful tools in the development of novel therapeutic strategies for the treatment of the diseases

Induction of cyclooxygenase-2 messenger RNA after transient and permanent middle cerebral artery occlusion in rats: comparison with c-fos messenger RNA by using in situ hybridization

Object. Recently, two different cyclooxygenase (COX) genes, COX-1 and -2, were identified. In this study, topographic and chronological profiles of COX-2 messenger (m)RNA and c-fos mRNA expression were investigated using in situ hybridization after focal cerebral ischemia.Methods. Rats undergoing permanent ischemia were decapitated at 30 and 90 minutes and at 2, 4, 8, and 24 hours after middle cerebral artery (MCA) occlusion, and rats undergoing transient ischemia were decapitated at 4, 8, and 24 hours after MCA occlusion that lasted for either 30 or 90 minutes. After brief transient MCA occlusion, c-fos mRNA was induced in the whole MCA territory, adjacent cortex (cingulate cortex), and distant brain regions such as the hippocampus and substantia nigra. In contrast, COX-2 mRNA was not induced in the ischemic core (lateral striatum) but only in the penumbral area (MCA cortex). Long transient and permanent MCA occlusion did not induce c-fos and COX-2 mRNAs in the ischemic core but strongly induced both mRNAs in the penumbral area (medial striatum and periphery of MCA cortex) and adjacent cortex (cingulate cortex). In brain regions distant from the ischemic territory, although c-fos mRNA was induced in the thalamus, substantia nigra, and hippocampus after extended transient and permanent occlusion, COX-2 mRNA was only induced in the bilateral hippocampi. The induction of COX-2 mRNA persisted in all locations even at 24 hours after MCA occlusion.Conclusions. The distribution of COX-2 mRNA induction was apparently different from that of c-fos mRNA after MCA occlusion. These results pertaining to COX-2 mRNA agree well with the previous observations of changes in prostaglandin metabolism induced by focal cerebral ischemia. However, whether this induction of the COX-2 gene contributes to the histopathological outcome of cerebral ischemia remains to be elucidated.</jats:p